/* Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.flowable.variable.service.impl.el;

import java.util.Collection;
import java.util.Collections;
import java.util.Map;
import java.util.Set;

import org.flowable.variable.api.delegate.VariableScope;
import org.flowable.variable.api.persistence.entity.VariableInstance;

/**
 * Variable-scope only used to resolve variables when NO execution is active but expression-resolving is needed. This occurs eg. when start-form properties have default's defined. Even though
 * variables are not available yet, expressions should be resolved anyway.
 * 
 * @author Frederik Heremans
 * @author Joram Barrez
 */
public class NoExecutionVariableScope implements VariableScope {

    private static final NoExecutionVariableScope INSTANCE = new NoExecutionVariableScope();

    /**
     * Since a {@link NoExecutionVariableScope} has no state, it's safe to use the same instance to prevent too many useless instances created.
     */
    public static NoExecutionVariableScope getSharedInstance() {
        return INSTANCE;
    }

    @SuppressWarnings("unchecked")
    @Override
    public Map<String, Object> getVariables() {
        return Collections.EMPTY_MAP;
    }

    @SuppressWarnings("unchecked")
    @Override
    public Map<String, Object> getVariablesLocal() {
        return Collections.EMPTY_MAP;
    }

    @SuppressWarnings("unchecked")
    @Override
    public Map<String, Object> getVariables(Collection<String> variableNames) {
        return Collections.EMPTY_MAP;
    }

    @SuppressWarnings("unchecked")
    @Override
    public Map<String, Object> getVariables(Collection<String> variableNames, boolean fetchAllVariables) {
        return Collections.EMPTY_MAP;
    }

    @SuppressWarnings("unchecked")
    @Override
    public Map<String, Object> getVariablesLocal(Collection<String> variableNames) {
        return Collections.EMPTY_MAP;
    }

    @SuppressWarnings("unchecked")
    @Override
    public Map<String, Object> getVariablesLocal(Collection<String> variableNames, boolean fetchAllVariables) {
        return Collections.EMPTY_MAP;
    }

    @Override
    public Object getVariable(String variableName) {
        return null;
    }

    @Override
    public Object getVariable(String variableName, boolean fetchAllVariables) {
        return null;
    }

    @Override
    public Object getVariableLocal(String variableName) {
        return null;
    }

    @Override
    public Object getVariableLocal(String variableName, boolean fetchAllVariables) {
        return null;
    }

    @Override
    public <T> T getVariable(String variableName, Class<T> variableClass) {
        return null;
    }

    @Override
    public <T> T getVariableLocal(String variableName, Class<T> variableClass) {
        return null;
    }

    @Override
    public Map<String, VariableInstance> getVariableInstances() {
        return null;
    }

    @Override
    public Map<String, VariableInstance> getVariableInstances(Collection<String> variableNames) {
        return null;
    }

    @Override
    public Map<String, VariableInstance> getVariableInstances(Collection<String> variableNames, boolean fetchAllVariables) {
        return null;
    }

    @Override
    public Map<String, VariableInstance> getVariableInstancesLocal() {
        return null;
    }

    @Override
    public Map<String, VariableInstance> getVariableInstancesLocal(Collection<String> variableNames) {
        return null;
    }

    @Override
    public Map<String, VariableInstance> getVariableInstancesLocal(Collection<String> variableNames, boolean fetchAllVariables) {
        return null;
    }

    @Override
    public VariableInstance getVariableInstance(String variableName) {
        return null;
    }

    @Override
    public VariableInstance getVariableInstance(String variableName, boolean fetchAllVariables) {
        return null;
    }

    @Override
    public VariableInstance getVariableInstanceLocal(String variableName) {
        return null;
    }

    @Override
    public VariableInstance getVariableInstanceLocal(String variableName, boolean fetchAllVariables) {
        return null;
    }

    @SuppressWarnings("unchecked")
    @Override
    public Set<String> getVariableNames() {
        return Collections.EMPTY_SET;
    }

    @Override
    public Set<String> getVariableNamesLocal() {
        return null;
    }

    @Override
    public void setVariable(String variableName, Object value) {
        throw new UnsupportedOperationException("No execution active, no variables can be set");
    }

    @Override
    public void setVariable(String variableName, Object value, boolean fetchAllVariables) {
        throw new UnsupportedOperationException("No execution active, no variables can be set");
    }

    @Override
    public Object setVariableLocal(String variableName, Object value) {
        throw new UnsupportedOperationException("No execution active, no variables can be set");
    }

    @Override
    public Object setVariableLocal(String variableName, Object value, boolean fetchAllVariables) {
        throw new UnsupportedOperationException("No execution active, no variables can be set");
    }
    
    @Override
    public void setVariables(Map<String, ? extends Object> variables) {
        throw new UnsupportedOperationException("No execution active, no variables can be set");
    }

    @Override
    public void setVariablesLocal(Map<String, ? extends Object> variables) {
        throw new UnsupportedOperationException("No execution active, no variables can be set");
    }

    @Override
    public boolean hasVariables() {
        return false;
    }

    @Override
    public boolean hasVariablesLocal() {
        return false;
    }

    @Override
    public boolean hasVariable(String variableName) {
        return false;
    }

    @Override
    public boolean hasVariableLocal(String variableName) {
        return false;
    }

    public void createVariableLocal(String variableName, Object value) {
        throw new UnsupportedOperationException("No execution active, no variables can be created");
    }

    public void createVariablesLocal(Map<String, ? extends Object> variables) {
        throw new UnsupportedOperationException("No execution active, no variables can be created");
    }

    @Override
    public void removeVariable(String variableName) {
        throw new UnsupportedOperationException("No execution active, no variables can be removed");
    }

    @Override
    public void removeVariableLocal(String variableName) {
        throw new UnsupportedOperationException("No execution active, no variables can be removed");
    }

    @Override
    public void removeVariables() {
        throw new UnsupportedOperationException("No execution active, no variables can be removed");
    }

    @Override
    public void removeVariablesLocal() {
        throw new UnsupportedOperationException("No execution active, no variables can be removed");
    }

    @Override
    public void removeVariables(Collection<String> variableNames) {
        throw new UnsupportedOperationException("No execution active, no variables can be removed");
    }

    @Override
    public void removeVariablesLocal(Collection<String> variableNames) {
        throw new UnsupportedOperationException("No execution active, no variables can be removed");
    }

    @Override
    public void setTransientVariablesLocal(Map<String, Object> transientVariables) {
        throw new UnsupportedOperationException("No execution active, no variables can be set");
    }

    @Override
    public void setTransientVariableLocal(String variableName, Object variableValue) {
        throw new UnsupportedOperationException("No execution active, no variables can be set");
    }

    @Override
    public void setTransientVariables(Map<String, Object> transientVariables) {
        throw new UnsupportedOperationException("No execution active, no variables can be set");
    }

    @Override
    public void setTransientVariable(String variableName, Object variableValue) {
        throw new UnsupportedOperationException("No execution active, no variables can be set");
    }

    @Override
    public Object getTransientVariableLocal(String variableName) {
        return null;
    }

    @Override
    public Map<String, Object> getTransientVariablesLocal() {
        return null;
    }

    @Override
    public Object getTransientVariable(String variableName) {
        return null;
    }

    @Override
    public Map<String, Object> getTransientVariables() {
        return null;
    }

    @Override
    public void removeTransientVariableLocal(String variableName) {
        throw new UnsupportedOperationException("No execution active, no variables can be removed");
    }

    @Override
    public void removeTransientVariablesLocal() {
        throw new UnsupportedOperationException("No execution active, no variables can be removed");
    }

    @Override
    public void removeTransientVariable(String variableName) {
        throw new UnsupportedOperationException("No execution active, no variables can be removed");
    }

    @Override
    public void removeTransientVariables() {
        throw new UnsupportedOperationException("No execution active, no variables can be removed");
    }

    @Override
    public String getTenantId() {
        return null;
    }
}
